This invention relates to multi-axled traction vehicles, and more particularly it relates to means for detecting a locked axle condition on such a vehicle.
A traction vehicle such as a railway locomotive has a plurality of axles for driving the wheels of the vehicle along a track. The axles are mounted in groups of two or three on two or more "trucks" with the vehicle itself mounted on the trucks. In operation one of the axles may become locked against rotation due to seizure of bearings or the like. If this condition were not promptly detected and corrected, it could have a number of adverse consequences, including the wearing of flat spots on the wheels. In order to minimize such difficulties, it is desirable to warn the engineer of the locomotive that a locked axle or a sliding wheel condition has occurred.
Accordingly, a general objective of the present invention is to provide an improved scheme on a multi-axle traction vehicle for detecting when one of the axles is locked.
It has heretofore been proposed to detect a locked axle condition on a multi-axle traction vehicle by suitably connecting speed detectors to monitor axle speed and to produce a warning signal when the sensed speed of any one of the axles is less than a predetermined first threshold level. Such a system is described in U.S. Pat. No. 4,031,509 granted on June 21, 1977 to E. S. Matulevich and assigned to the General Electric Company. This patented system also describes a "no-motion" arrangement which disables the system, thereby preventing it from producing the warning signal, except when the speed of the vehicle exceeds a second predetermined threshold indicating that the vehicle is in motion.
Although the above-described system is identified as a locked axle detector, it also functions as a wheel slip detector whenever the vehicle is moving at a speed less than the first predetermined threshold. At that speed a wheelslip, if it results in an axle exceeding the speed set by the second threshold, will cause the system to generate a warning signal. Because of its dual function as a locked axle and wheel slip detector, this system is susceptible to false signals. For example, a transient signal in any one of the speed detector circuits may cause a warning signal to be generated. Although a time delay is incorporated in the system to minimize the chances of producing a false warning signal, the adverse environment in a traction vehicle produces transient signals which may trigger the locked axle detection circuit.
It is an object of the present invention to provide a locked axle detection system which reduces the possibility of a false indication without detrimentally affecting the sensitivity of the system.